Distribution of First Instar Gypsy Moths (Lepidoptera: Lymantriidae) Among Saplings of Four Tree Species Common in the Great Lakes Region

We examined the inter-tree distribution of first instar gypsy moth larvae under natural dispersal conditions in the field in Michigan in 1991. The study focused on saplings of northern red oak (Quercus rubra), white oak (Q. alba), red maple (Acer rubrum), and witch-hazel (Hamamelis virginiana), which are common understory components of forests in the Great Lakes region. Large-volume trees with foliage that is well-developed early in the spring should provide an excellent surface area for catching newly-hatched gypsy moth larvae, which are randomly dispersed by wind in the spring around the time of leaf flush or shortly thereafter. Comparing across tree species in our study, red maples had the largest crown volumes and wellflushed leaf material, but very few larvae were found on these trees at both sampling times in mid-May. Despite the lack of larvae on red maple, these trees were liberally covered with gypsy moth silk, indicating that many larvae landed on these plants but left rapidly when they apparently found the trees to be an unacceptable food source. Among the other three tree species, patterns of larval distribution reflected levels of host phenological development during both sampling periods, with more insects occurring on tree species that had more advanced leaf development. The highest numbers of larvae were found on northern red oak and witch-hazel. Intermediate num­bers of insects were present on white oak. Trends in insect distribution also paralleled patterns seen in tree phenology across slope gradients. Defoliation ratings corresponded well to measures of first instar presence for each tree species. Northern red oak and witch-hazel trees experienced more early defoliation on average than did red maple and white oak. For those tree species that are acceptable hosts of the gypsy moth, average level of phenological development for a given tree, species, or forest stand at the time of larval dispersal can be an important predictor of plant or stand susceptibility to gypsy moth establishment and subsequent defoliation

Estimating the Number of Eggs per Egg Mass of the Forest Tent Caterpillar, Malacosoma Disstria (Lepidoptera: Lasiocampidae)

Calculation of the number of eggs per egg mass of the forest tent caterpillar, Malacosoma disstria Hiibner, is required in survey and population studies. Eggs are usually laid in cylindrical masses around twigs of trees. Hodson (1941) determined the number of eggs in egg masses of the forest tent caterpillar by counting the number of eggs around the circumference and multiplying by the number of rows. This technique is apparently reliable for comparative counts, but because the eggs are frequently laid in oblique rather than straight rows on the twig, counts of both length and circumference are subject to error. In addition, adjacent rows are often offset to form a honeycomb pattern which leads to inaccuracies in length and circumference counts. Because of these shortcomings, we developed a quicker and more accurate method not subject to the effects of oblique or honeycomb egg patterns

Differences in Emergence Date and Size Between the Sexes of \u3ci\u3eMalacosoma Americanum\u3c/i\u3e the Eastern Tent Caterpillar (Lepidoptera: Lasiocampidae)

Malacosoma americanum males were smaller and began to pupate earlier than females. Since the sexes spent the same amount of time as pupae, males also emerged earlier. The adaptive significance of these results is discussed. Emergence data revealed an interesting sidelight; no moths emerged from cocoons inside tents

The Role of Tree Clinics in Urban Forestry

A tree clinic analyzes tree problems and recommends appropriate actions to the public. The objective of tree clinics is to inform the citizen about urban trees. This paper is based on the experiences of 30 tree clinics held in Ann Arbor during the last eight years. The ingredients necessary for a successful tree clinic are discussed: (I) active sponsor, (2) suitable date and time, (3) good location, (4) proper publicity, (5) diversified experts, (6) proper organization, (7) sizable public turnout, and (8) follow-up publicity and acknowledgments

Introduction of Parasites of the Larch Sawfly in Minnesota

Olesicampe benefactor Hinz and the Bavarian strain of Mesoleius tenthredinis Morley, European ichneunionid parasites of the larch sawfly, Pristiphora erichsonii (Hartig), were introduced into northern Minnesota from Manitoba in 1971 and 1972. Both species are now established. There was also natural spread of 0. benefactor into Minnesota from Manitoba releases in 1961 at a point ca. 200 miles northwest of the Minnesota plots

Impact of the Spruce Budworm (Lepidoptera: Tortricidae) on the Ottawa and Hiawatha National Forests, 1978-1980

The Michigan Impact Plot System was established during 1978 and 1979 to obtain a data base for quantifying the impact of the spruce budworm in the Ottawa and Hiawatha National Forests. The formulae used to estimate the mean, total, and associated standard errors of the various parameters at the national forest and forest district levels are presented. We present the 1978, 1979, and 1980 impact data for the following parameters; percent mortality, total dead volume. dead volume per ha, live volume per ha, defoliation ranking, frequency and extent of top-kill, and incidence of spruce budworm feeding on saplings and regenera- tion. Statistics from an annual inventory of 108 composite ground sampling units (CGSU) in 1978, and 136 CGSU\u27s in 1979 and 1980 provide a more precise estimate ofthe impact of the spruce budworm in Michigan\u27s Upper Peninsula than ha~ been available to date

The Economics of Spruce Budworm Outbreaks in the Lake States: An Overview

Economic effects of spruce budworm outbreaks in the Lake States were examined. The recent outbreak caused spruce and fir mortality on 420 thousand ha (I.OS million acres) of commercial forest land in the Lake States. Two models of Lake States spruce-fir markets were developed. A Static Economic Model established the nature of the Lake States spruce-fir market and a Comparative Static Model examined changes brought about by spruce budworm outbreaks. Outbreaks result in short-run supply shifts which probably decrease total revenue to stumpage owners but do not affect demand. The magnitude of long-run impacts were dependent on developing Lake States markets and forest management techniques. Further research is necessary on the value of short-run losses to stumpage owners so that the costs of forest management can be compared with outbreak losses. Long-run shifts in demand can be facilitated by attracting new industry to the area, developing new markets for the spruce-fir resource, and demonstrating that the spruce-fir resource can provide a continuous fiber source in the future. These shifts would provide the price incentives that land managers require to undertake intensive forest management. Research on the development of new markets for the spruce-fir resource is needed. As markets develop, the long-run impacts become less severe. Technology transfer programs already exist to aid land managers in developing management strategies to increase yields of spruce-fir and minimize outbreak impact

Distribution of First Instar Gypsy Moths (Lepidoptera: Lymantriidae) Among Saplings of Four Tree Species Common in the Great Lakes Region

We examined the inter-tree distribution of first instar gypsy moth larvae under natural dispersal conditions in the field in Michigan in 1991. The study focused on saplings of northern red oak (Quercus rubra), white oak (Q. alba), red maple (Acer rubrum), and witch-hazel (Hamamelis virginiana), which are common understory components of forests in the Great Lakes region. Large-volume trees with foliage that is well-developed early in the spring should provide an excellent surface area for catching newly-hatched gypsy moth larvae, which are randomly dispersed by wind in the spring around the time of leaf flush or shortly thereafter. Comparing across tree species in our study, red maples had the largest crown volumes and wellflushed leaf material, but very few larvae were found on these trees at both sampling times in mid-May. Despite the lack of larvae on red maple, these trees were liberally covered with gypsy moth silk, indicating that many larvae landed on these plants but left rapidly when they apparently found the trees to be an unacceptable food source. Among the other three tree species, patterns of larval distribution reflected levels of host phenological development during both sampling periods, with more insects occurring on tree species that had more advanced leaf development. The highest numbers of larvae were found on northern red oak and witch-hazel. Intermediate num­bers of insects were present on white oak. Trends in insect distribution also paralleled patterns seen in tree phenology across slope gradients. Defoliation ratings corresponded well to measures of first instar presence for each tree species. Northern red oak and witch-hazel trees experienced more early defoliation on average than did red maple and white oak. For those tree species that are acceptable hosts of the gypsy moth, average level of phenological development for a given tree, species, or forest stand at the time of larval dispersal can be an important predictor of plant or stand susceptibility to gypsy moth establishment and subsequent defoliation

Differences in Emergence Date and Size Between the Sexes of \u3ci\u3eMalacosoma Americanum\u3c/i\u3e the Eastern Tent Caterpillar (Lepidoptera: Lasiocampidae)

Malacosoma americanum males were smaller and began to pupate earlier than females. Since the sexes spent the same amount of time as pupae, males also emerged earlier. The adaptive significance of these results is discussed. Emergence data revealed an interesting sidelight; no moths emerged from cocoons inside tents

Sea state and rain: a second take on dual-frequency altimetry

TOPEX and Jason were the first two dual-frequency altimeters in space, with both operating at Ku- and C-band. Each thus gives two measurements of the normalized backscatter, sigma0, (from which wind speed is calculated) and two estimates of wave height. Departures from a well-defined relationship between the Ku- and C-band sigma0 values give an indication of rain.This paper investigates differences between the two instruments using data from Jason's verification phase. Jason's Ku-band estimates of wave height are ~1.8% less than TOPEX's, whereas its sigma0 values are higher. When these effects have been removed the root mean square (r.m.s.) mismatch between TOPEX and Jason's Ku-band observations is close to that for TOPEX's observations at its two frequencies, and the changes in sigma0 with varying wave height conditions are the same for the two altimeters. Rain flagging and quantitative estimates of rain rate are both based on the atmospheric attenuation derived from the sigma0 measurements at the two frequencies. The attenuation estimates of TOPEX and Jason agree very well, and a threshold of -0.5 dB is effective at removing the majority of spurious data records from the Jason GDRs. In the high sigma0 regime, anomalous data can be cause by processes other than rain. Consequently, for these low wind conditions, neither can reliable rain detection be based on altimetry alone, nor can a generic rain flag be expected to remove all suspect data